A wide variety of mechanisms have been designed and developed for translating motion from one element to another. The present mechanism relates to a structure for actuating a bail between first and second positions usually along a portion of an arc which may comprise some fifty or sixty degrees of arc to eighty or one hundred degrees. Such mechanisms may appear in varied devices, such as camera shutters, typewriter mechanisms, display devices, factory machines, and extension levers for actuating recessed light switches or circuit breakers.
The invention is specifically directed to the reciprocal actuation of a bail in response to the actuation of a lever. In some types of linkages, the bail may have to be driven from a first position to a second position. In other types of systems, the bail may be acted upon by auxiliary forces, so that once the bail is urged from an initial position to a critical position, the auxiliary forces urge the bail towards its destination independent of the force of the actuating linkage. In such systems, it is sometimes desirable to allow at least some free travel of the bail once it has reached the critical point. In some structures, it is desirable to have the actuating cam in intimate contact with the bail when the bail is at either at rest position so that tactile feedback can be provided to indicate the bail position. Phrased differently, it is sometimes desirable to have no "lost motion" of the actuating lever when the bail is in an at rest position. However, as mentioned above, there are mechanisms wherein it is desirable to allow the bail to have at least some free motion independent of the actuating cam during at least part of the time that the bail is intermediate of its at rest positions.
The structure disclosed herein is directed to mechanisms of the class which require no lost motion of the actuating lever when the bail is at its at rest positions and which requires at least some free motion of the bail when it is intermediate of its at rest positions. However, the invention could readily be adapted to an inverse application wherein at least some lost motion of the actuating lever is required when the bail is at its at rest positions and which requires reduced free motion of the bail when it is intermediate of its at rest positions.
An example of a practical structure having the first requirements is that of a circuit breaker within an enclosure and actuated by an auxiliary lever extending through a wall of the enclosure. When the circuit breaker is at either at rest position, the auxiliary lever should have minimum free motion so that, by tactile feedback, one manipulating the auxiliary lever could sense the position of the circuit breaker. When the circuit breaker is being moved from its closed circuit to its open circuit position, it is desirable for the circuit breaker arm to be allowed at least some free motion during the time the contacts are actually being opened.
A variety of linkages have been developed for providing features similar to those described. Such prior art linkages have frequently employed a plurality of parts including some or all of the following: auxiliary springs, auxiliary lost motion structures, knuckles, separate on and off levers, and a variety of other structures.